James, you've got copies in your tree. Some of those copies have
sources that are either

- in revision trees from before the earliest revision in your
dumpfile, or

- in locations not included in your dump.

Depending on what kind of activity has been going on in your
repository, non-complete dumpfiles can be very complex. Whenever you
dump less than the whole repository, you can run into trouble.

Does this clarify what the problem is?

It's not clear what 'svnadmin dump' should do about this. Including
data in the dump (the copy sources) that was not requested in the dump
has its own problems. After all, in order for the new repository to
reflect the copy history accurately, it would have to put that source
data somewhere in the new repository too. But where? You didn't ask
for it to be dumped; logically, it should not be carried across when
you load the dumpfile.

Sorry, I'm not trying to say "talk to the hand" :-), I'm just not sure
what the right solution is. You might be better off just importing a
tree than trying to load history from an incomplete dumpfile.